The present invention relates to a sheet finishing apparatus in which a plurality of recording sheets, on which images are recorded by a copier, a printer or a similar apparatus, are sorted for each predetermined number of sheets, and are stacked onto a delivery tray.
When a sheet finishing apparatus is provided by which a plurality of copied sheets are automatically sorted for each predetermined number of sheets, it is very convenient for the operator because no additional operation is necessary for sheet finishing, in a case (the sort mode) where plural sets of prints are successively delivered, wherein a single set of prints is formed of a plurality of sheets on which images are recorded by an image forming apparatus such as a copier, a printer or a similar apparatus, or in a case (the group mode) where plural numbers of sheets are successively copied corresponding to the same single document, and plural sets of sheets are copied with respect to a plurality of documents.
Further, as an apparatus to collate a plurality of sheets, which are delivered from the image forming apparatus and on which images have been recorded, for each copied set and to staple it by a stapler, a sheet finishing apparatus, which is called a finisher, is used. Functions of the finisher are connected to those of the image forming apparatus, and the finisher is driven corresponding to the sequence operation of the copy process. In this finisher, there is a finisher, also provided with a sheet sorting means (a shift means) other than a stapler. Sheets, which require no stapling processing, are shifted in the direction perpendicular to the sheet conveyance direction, for each set of copy sheets by the shift means, and are delivered onto the delivery tray.
As a sheet sorting apparatus for this purpose, a sorting tray apparatus is widely known in which a delivery tray can be moved perpendicular to the sheet delivery direction; and a delivery sheet tray is moved every time when a single set of a predetermined number of sheets has been delivered, so that each set of a predetermined number of sheets is alternately stacked on the tray (Japanese Patent Publication Open to Public Inspection No. 217464/1986, and others). In this case, an eccentric cam or similar parts are used for the movement of the delivery sheet tray.
Further, the following sorting tray apparatus is also widely known: the delivery sheet tray is rotated by a predetermined angle in the tray surface plane, so that each set of sheets is alternately stacked while each set of sheets is shifted from each other by a predetermined angle.
Other than the above devices, a sorter is also used in which a plurality of delivery sheet trays (bins) are provided and a delivery sheet tray, opposite to the delivery port, is switched for a predetermined number of sheets.
In each of above apparatus, it is required to move the delivery sheet tray while sheets are stacked on the delivery sheet tray. Accordingly, there are disadvantages in which the apparatus becomes completed; the size of the apparatus is increased; and the power consumption is increased, etc. Especially, when a delivery sheet tray, on which about 2000 sheets can be stacked, is shifted, a large power driving motor is necessary. Further, there are problems in which, when a delivery sheet tray, on which sheets are stacked, is moved perpendicular to the delivery direction, sheets stacked on the delivery sheet tray collapse and become irregular, so that sorting is very difficult, or sheets fall down from the delivery sheet tray.
Still further, a sheet sorting apparatus is widely known in which sheets, delivered from a pair of discharging rollers of the image forming apparatus onto a delivery sheet holder, are respectively shifted from each other for each predetermined number of sheets and stacked on the delivery sheet holder, and sheets are sorted, when a pair of discharging rollers to pressure-contact and hold the sheet are reciprocally moved along the axis by a predetermined distance (Japanese Patent Publication Open to Public Inspection 33459/1986). In this sheet sorting apparatus, there is a problem in which a driving transmission mechanism becomes complicated, because a pair of discharging rollers by which sheets are held during delivering, and which are in pressure-contact with each other and are rotated, are moved along the axis.
Still further, the present invention relates to a sheet finishing apparatus which is provided with a stapling means (a stapler) and by which recording sheets (sheets), on which images are recorded by the image forming apparatus, are automatically finishing-processed and delivered, and specifically relates to a manual operation and automatic position control of the stapling means.
With respect to an image forming apparatus in which copying can be processed at a high speed, a finisher is required which can follow the speed, perform its functions, and conduct high speed processing.
Such a finisher which can conduct high speed processing, has already been disclosed in Japanese Patent Publication Open to Public Inspection Nos. 142359/1985, 158463/1985, 239169/1987, 288002/1987, 267667/1988, 276691/1990, 276692/1990, and Japanese Patent Publication No. 41991/1993.
Sheets, on which images have been recorded and delivered from the image forming apparatus main body, are successively stacked on an intermediate stacker while being aligned. After a single set of sheets has been accommodated in the intermediate stacker, sheet finishing such as stapling, is conducted, and sets of stapled sheets are conveyed by a delivery belt provided in a bottom portion of the intermediate stacker. Further, the sheets are held by a sheet holding and delivery means such as a pair of upper and lower discharging rollers, and delivered onto a delivery sheet tray.
An image forming apparatus provided with a sheet finishing unit, disclosed in Japanese patent Publication Open to Public Inspection No. 277591/1991, has the fist staple mode in which one portion is stapled which is separated from an end of a side of the recording sheet by a predetermined distance along the side, and the second staple mode in which two portions are stapled which are separated from each other along one side of the recording sheet by a predetermined distance, on both sides of the central portion of the side of the recording sheet.
In a conventional sheet finishing apparatus, staple units are fixed on the base frame, and thereby, in staple-processing of sets of sheets, when a failure such as buckling of a staple pin occurs, it is difficult to take out the failed set of sheets or the failed staple pin.
In the conventional sheet finishing apparatus, a staple pin is pinned in parallel to a side of the recording sheet in the first staple mode for one portion stapling and also the second staple mode for two portion stapling, as shown in the above-described Japanese Patent Publication Open to Public Inspection 177591/1991. However, in the first staple mode for one portion stapling, a staple pin is pinned at one portion of a corner of a set of sheets in parallel to a side of the recording sheet. Thereby, when a set of sheets is opened for reading, there is a possibility in which a sheet is broken at a stapled portion. Accordingly, when one portion of a corner of a set of sheets is stapled by a staple means, stapling is preferably conducted diagonally (for example, by 45.degree.) with respect to a width of sheets, for convenience of use for opening a page of sheets. Further, when two portions near the central portion of the width of sheets are stapled, stapling is preferably conducted on two portions parallel to the direction of the width of sheet.